Although Karlovic hit a world record 78 aces, he was unable to prevent Stepanek carving out the only break for a 15-14 lead.

"Everything is known about Karlovic. He really has a phenomenal serve. That is why the only thing I could do was to wait patiently for my chance," said Stepanek, the world number 16.

"Mentally I was very strong and calm and it was decisive in this match."

The match was just one minute short of becoming only the fourth Davis Cup rubber over six hours while the total number of games (82) equalled the highest number in a Davis Cup rubber since the tiebreaker was introduced.

It was just three short of the overall record for a World Group tie.

In Friday's second rubber Marin Cilic faces Tomas Berdych.

The eventual winners of the tie will face either defending champions Spain or Israel in December's final.